1. Technical Field
The technical field relates to an imaging apparatus and an interchangeable lens that include lenses movable in an optical axis direction. More particularly, the technical field relates to a technique for detecting a loss of synchronism of a motor that drives a lens in an imaging apparatus and an interchangeable lens.
2. Related Art
Conventionally, there exists an imaging apparatus that drives a focus lens by a motor. Such a movable lens is driven by, for example, a stepping motor. When the movable lens is driven by a stepping motor, there is a problem that, when an external shock is applied to the stepping motor, the stepping motor loses synchronism and thus cannot move the movable lens to a desired position. Accordingly, there is a need to, for example, detect a loss of synchronism of the stepping motor, and move the lens to a predetermined reference position when a loss of synchronism is detected.
For a prior art document pertaining to techniques for detecting a loss of synchronism of a stepping motor that drives a movable lens, there is JP 07-199033 A. A drive apparatus of a member for driving an optical system described in JP 07-199033A detects a loss of synchronism of a stepping motor, based on the loss of output pulses from a photointerrupter.
However, resolution of the photointerrupter is not so high, and thus a loss of synchronism of the stepping motor cannot be detected with high accuracy by the technique described in JP 07-199033 A.
Meanwhile, for a macro lens that allows for shooting with a focal length ranging from infinity to 1:1 close up, a plurality of focus lens groups are allowed to move independently of each other. With such a configuration, miniaturization can be achieved while the focal length is changed greatly.
In such a macro lens, when a loss of synchronism occurs in even one focus lens group, even if focus can be achieved, the macro lens cannot realize it's maximum potential. Hence, detection of a loss of synchronism becomes more important.
To solve the above problem, an imaging apparatus and an interchangeable lens are provided that are capable of detecting a loss of synchronism of a motor with high accuracy.